Various devices are well known for controlling cursor movement over a computer display screen of a computer and for signaling a choice of computer command identified by the position of the cursor on the display screen menu. One such device is a "mouse" which has a ball on its underside that is rolled over a horizontal surface, with the x- and y-axis components of movement being sensed and transmitted through a connecting cable to a serial input port of the computer. The signal to the computer is varied in accordance with the amount and direction of movement of the mouse ball, and causes the cursor on the display screen to have a corresponding movement. Two "mouse" or "click" buttons located on the top of the mouse at the forward end permit the computer operator to input a selection or other command to the computer (the command typically being indicated by the position of the cursor on a displayed menu) upon pressing one or the other or both buttons, depending upon the software associated with the device. Such a device, which is separate from the computer console and keyboard and requires a connection to a computer port, requires a flat, horizontal surface, and for operation of the mouse, the computer operator must completely remove one hand from the computer keyboard.
Another cursor controlling and signalling mechanism is a "joystick" which like the mouse is completely separated from the computer console and keyboard. The joystick is typically an elongated stick which extends upwardly from a base that is connected to the computer console by means of a cable. The joystick is operated by tilting the upstanding stick in various directions to cause the cursor or other display element to move in a direction and usually at a speed corresponding to the direction and pressure exerted on the stick by the computer operator. The operation of a joystick, however, frequently requires that both hands be removed from the computer keyboard, one hand to hold the base while the other manipulates the joystick. A "click" button is usually located on the joystick itself. Although a mouse or a joystick can be used with a portable "laptop" or "notebook" size computers, such devices are cumbersome, must be carried separately and connected to the computer prior to use, and are not suitable for operation during travel.
Another type of cursor controlling device is a "trackball". This device, which in essence is an inverted mouse, includes a rotatable ball mounted within a housing. The ball is rotated by a finger, thumb or palm of the computer operator, and the x- and y-components of movement are sensed and input into the computer to cause corresponding movement of the cursor across the display screen. "Mouse or "click" buttons are usually located on the trackball housing, although with some models the selection signal is input by pressing the "enter" key on the standard keyboard. This type of pointing device has been found useful in conjunction with portable computers because it can be temporarily affixed to one side of the computer case for manipulation by one hand of the computer operator. However, even though trackball devices can be removably attached to the computer case, they still require attachment prior to use and removal after use and they do not have an ergonomically positioned set of "click" buttons.
One manufacturer of portable laptop computers, recognizing the need for placing the cursor controlling device in a permanent and more convenient location, installed a small, stubby, buttonlike joystick centrally among the keys of the computer keyboard, specifically at the juncture of the "g", "h" and "b" keys of the standard "QWERTY" keyboard. The joystick was sensitive to lateral pressure, the magnitude and direction of which were sensed and input into the computer to cause movement of the cursor, and the speed and direction of cursor movement corresponded to the magnitude and direction of pressure on the joystick. That manufacturer also provided two upwardly extending "mouse" or "click" buttons immediately below the space bar. The problem with that arrangement was that the stubby joystick was in the middle of the keyboard keys where it would be constantly hit by the fingers during normal keyboard operation, and requiring users to rotate their hand to an uncomfortable and unnatural position to use the joystick. Moreover, the "click" buttons were positioned so that it was awkward to operate them accurately using the side of the thumb rather the end of the thumb or a finger and yet they could be accidentally hit and actuated by the operator when operating the space bar or while the hands are at rest. That arrangement was not comfortable for the user who could be and many times would be required to operate the pointing device for extended periods of time without using the keyboard. Additionally, in a compact computer, room on the keyboard top is at a premium.